In recent years, vehicles equipped with an automatic stop and restart control system for an engine have been increasing for the purpose of improving fuel economy, reducing exhaust emissions, or the like. A typical automatic stop and restart control system of the related art is configured so as to automatically stop an engine by stopping fuel injection and spark ignition when a driver stops a vehicle, and thereafter, to restart the engine by automatically energizing a starter or a motor serving as the starter and cranking the engine when the driver performs an operation (a brake release operation, an accelerator depression operation, or the like) to start the vehicle.
Further, lately, executed is control of temporarily stopping an engine when a certain predetermined condition is satisfied during traveling, disconnecting a clutch, interposed between an automatic transmission and the engine, to drive a vehicle by inertia, and then, restarting the engine when a predetermined condition is satisfied, and re-fastening the clutch (hereinafter, referred to as engine stop and inertia traveling control). In this manner, it is possible to maintain vehicle speed by stopping the engine over a long period of time in the state of not depressing an accelerator pedal, so that improvement in fuel economy can be expected.
Such engine stop and inertia traveling control is described, for example, in JP 2007-291919 A (PTL 1). PTL 1 describes a technique of causing a vehicle to perform inertia traveling without starting generation of a driving force while the vehicle is traveling a downward slope when an inter-vehicle distance between a subject vehicle and a preceding vehicle becomes larger than a maximum inter-vehicle distance.